Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.25	6.139%	$234.8325	$234.83	$234.85	$234.80
Purchase #2	$35.56	8.465%	$38.5702	$38.57	$38.55	$38.60
Purchase #3	$197.97	6.835%	$211.5012	$211.50	$211.50	$211.50
Purchase #4	$80.84	11.835%	$90.4074	$90.41	$90.40	$90.40
Purchase #5	$238.27	12.819%	$268.8138	$268.81	$268.80	$268.80
Purchase #6	$103.31	8.350%	$111.9364	$111.94	$111.95	$111.90
Purchase #7	$173.90	11.637%	$194.1367	$194.14	$194.15	$194.10
7 purchase totals =	$1,051.10		$1,150.1982	$1,150.20	$1,150.20	$1,150.10